A retractable tail-lift of this type is disclosed e.g. by the Hydfalt 3 model range of the company Gerd Bär GmbH, Heilbronn.
Tail-lifts are mounted to lorries or trailers for loading and unloading them. Retractable tail-lifts are mounted to the chassis using a guiding mechanism and can be retracted completely under the body or chassis frame after folding the platform once or twice, such that they do not project at any location to the rear beyond the body to prevent any disturbance. Retractable tail-lifts of this type are used for vehicles with interchangeable bodies and for all vehicles which must dock onto loading/unloading regions of cold storage houses.
In the Hydfalt 3 model range, the guiding mechanism is formed by two guiding rails in which the lifting mechanism with one vertical carriage each is suspended, and can be slidably moved between the working position located behind the vehicle and the driving position located below the vehicle. Each carriage comprises a front guiding element with an upper sliding member which abuts on an upper guiding surface of the guiding rail, and a rear guiding element with a lower sliding member which abuts on a lower guiding surface of the guiding rail. The guidance is disposed inside the guiding rails to protect the guiding surfaces from dirt. The guiding rail may also be mounted at any location to the vehicle or to cross members, which facilitates dimensioning of the guiding rail. This technology also provides maintenance-free sliding guidance if the sliding partners are appropriately selected. These sliding guidances have the object to adopt the net weight of the lifting mechanism and the platform and slidingly transfer it to the guiding element during folding and unfolding. The guiding elements also have the object to assume horizontal guidance during forward and backward movement. The centrally acting displacement cylinder and the irregular friction must simultaneously provide horizontal guidance. The unfavorable leverages—the separation of the guiding elements and the center of gravity of the tail-lift—also produce large horizontal guiding forces. Since the sliding materials, which consist substantially of plastic material or plastic composite material, are subjected to wear, the sliding members of the Hydfalt 3 model range are suspended on the carriage to obtain even wear. Towards this end, the symmetric guiding construction has guiding elements of aluminium for the tension side as well as the pressure side on both sides of the carriage plate. This guiding elements comprise chambers which are open towards the bottom for receiving the sliding elements, and are commonly borne by a specially disposed bolt which penetrates through the carriage plate. This construction requires relatively high precision and expensive measures to protect the support and bolt from rust. Guiding surface is wasted on the pressure side of the carriage in the region of the carriage plate thickness. With this construction, the forces are deviated through the bolt into the carriage plate, thereby producing a very large internal bore surface which necessitates great material solidity. The carriage plate thickness must nevertheless be excessively thick. This conventional construction is therefore technically very demanding and therefore expensive.